If you are 19 years old, you can file an income tax return even if someone claims you as a dependent. However, if someone has a legal right to claim you as a dependent, even if they do not, you may not be able to claim certain exemptions on your own return.

Filing and Dependency Status

According to Internal Revenue Service Publication 929, you can file your own tax return regardless of your age or dependency status. If you are claimed as a dependent, you must file a tax return if you make $6,100 or more, as of publication. If you are not a dependent, the threshold is $10,000 for a single taxpayer. Just because you are filing your own return, however, does not mean you can take the $3,900 personal exemption you are normally entitled to. Moreover, if you are supporting someone else -- your own child, for example -- you may not be entitled to that exemption either.

Dependency Criteria

In most circumstances, once you reach the age of 19 your parent can no longer claim you as a dependent. A parent can only claim you as a dependent if you are 18 or younger. Therefore, if you file an income tax return when you're 19, unless you are a student, you can take the $3,900 personal exemption on your return. If you are a student, however, and living at home, a parent can claim you as a dependent until you are 24. The fact that your parents can claim you, even if they don't, means you cannot take the exemption yourself.

Loss of Other Exemptions

It may be that you support yourself and a dependent child while living at a parent's home. Even if you pay for room and board, if you are 19 and a student, you lose both your own $3,900 personal exemption and the $3,900 exemption you would otherwise have for a dependent child, because your student status means that a parent could claim you as a dependent, even if they do not. IRS Publication 17 states: "If you can be claimed as a dependent by another person, you cannot claim anyone else as a dependent. Even if you have a qualifying child or qualifying relative, you cannot claim that person as a dependent."

Phaseouts

In some instances, your parent cannot claim the dependent child exemption because of an IRS-mandated exemption phaseout based on income. As of publication, the phaseout for a married parent filing separately begins at $150,000. The exemption for that parent is reduced by 2 percent for every $2,500 of income above the $150,000 threshold. When that parent's income reaches $375,000, the phaseout reaches 100 percent. The IRS position is that your parent could have claimed the exemption except for the phaseout, and therefore, when you file your own return, you cannot claim a personal exemption for yourself or a dependent child you support.